The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Metal-air batteries, e.g., Li-air batteries, have gained much attention as energy storage systems due to their high energy densities, comparable to that of gasoline in theoretical values. An advantage of metal-air batteries is that oxygen is not stored in the cathode, but acquired free from ambient air during discharge. Typical known metal-air batteries utilize a non-aqueous electrolyte to avoid the intensive reaction between water and the metal, e.g., Li. For aqueous electrolytes, there needs to be a separator to separate the aqueous solution from the metal. Additionally, the material of such air cathodes must be impermeable to aqueous electrolytes so that the aqueous electrolyte stays in the cell. Generally, an air cathode for a rechargeable metal-air battery is multifunctional in that it must be permeable to oxygen gas from the ambient atmosphere and provide active sites or reaction zones for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). In order to fulfill these functions well, such air cathodes are typically a sheet-like component having opposite surfaces that are respectively exposed to the ambient atmosphere and to an aqueous electrolyte.
Such known metal-air electrochemical batteries with non-aqueous electrolytes are cathode-limited because the electrolytes cannot dissolve the solid metal oxide, e.g., lithium oxide, products, which clog the pores and choke the air breathing cathode. In addition, moisture in ambient air can degrade non-aqueous electrolytes and react with lithium metal causing self-discharge. These problems directly lead to a short life of non-aqueous Li-air battery.